Nanoparticulate matter on the order of hundreds of nanometers or less from anthropomorphic and natural origins has increased dramatically with modern manufacturing, pervasive use of consumer electronics, and in medical applications. Nanopollution is a generic name for all waste generated by nanodevices or during the nanomaterials manufacturing process. This kind of waste may be very dangerous because of its size. It may float in the air and might easily penetrate animal and plant cells causing unknown effects. Most human-made nanoparticles do not appear in nature, so living organisms may not have appropriate means to deal with nanowaste.
Particulates may typically be removed from a fluid using a physical filtering system. For example, in a heating-ventilation and air conditioning (HVAC) system, particulates may be removed using fiberglass or spun-bound filters, charged plates, or ceramic beads that are interposed in the fluid flow. In liquid fluids, various mechanical filters may be used to remove particulates from a liquid. However, a physical filtering system restricts the flow of the fluid resulting in higher energy costs for moving the fluid and frequent maintenance. Additionally, a physical filtering system may become easily clogged, requiring frequent changes.
One type of filterless cleaning system uses acoustic energy, particularly ultrasonic energy, to concentrate particles efficiently in fluids. The concept of using ultrasonic energy in fluids may be applied to flow cytometry, microfluidics, and other liquid phase applications. Ultrasonic energy may be used to separate out micron-size biological molecules, such as cells, etc., using fluid cavities on the order of millimeters. Acoustic energy systems, however, are bulky and have poor acoustic coupling between the acoustic cavity and the reflecting materials. Acoustic energy systems, are generally not usable for higher temperature processes such as combustion and gasification processes which typically produce significant amounts of nanoparticle pollution. Such systems also do not include tuning capabilities to focus the location of the concentrated particles to a collection site to account for variations in the particle size and/or variations which might occur in the system. Therefore, there remains a need for improved acoustic separation systems for nanoparticle removal.